One of important requisites for a next generation wireless access system is to support a high data rate requirement. To this end, many ongoing efforts are made to research and develop various technologies including MIMO (multiple input multiple output), CoMP (cooperative multiple point transmission), Relay and the like.
In a wireless access system of a related art, a single carrier is mainly considered despite setting bandwidths of uplink and downlink to differ from each other. For instance, a wireless communication is provided based on a single carrier as follows. First of all, the number of carrier(s) configuring each of the uplink and the downlink is 1. Secondly, a bandwidth of the uplink and a bandwidth of the downlink are symmetric to each other in general.
Therefore, in order meet a higher data rate requirement, Carrier Aggregation (CA)/Multiple Cells are introduced as the concept of bundling a multitude of bands into a single system. Each of the distributed bands in the carrier aggregation is designed to meet the basic requirements for enabling a system independently.
In this case, a carrier of a bandwidth unit capable of each independent operation can be named a component carrier (CC). In order to support an increasing transmission capacity, the recent 3GPP LTE-A or 802.16m continues to extend its bandwidth up to 20 MHz or higher. In doing so, at least one or more component carriers are aggregated to support a broadband. For instance, if a single component carrier supports a bandwidth of 5 MHz, 10 MHz or 20 MHz, it is able to support a system bandwidth up to maximum 100 MHz in a manner of bundling maximum 5 components together.